The applicant will continue recent work in the sponsor's laboratory on the corrinoid adenosylation pathway of Salmonella typhimurium. This pathway is essential for the synthesis of the essential human nutrient cobalamin. The applicant will use state of the art technology for the cloning and characterization of the gene encoding a key enzyme of this pathway, i.e., cob(l)alamin oxidoreductase. For this purpose, the applicant will isolate the enzyme to homogeneity to generate amino acid sequence information to be used in the isolation of the locus encoding this function in S. typhimurium. The student will apply sophisticated genetic and biochemical techniques in the performance of her work Item 33 of this application describes in detail all the resources available to the applicant for the pursuit of her project. During the course of her Ph.D. work, the applicant will make use of the Fermentation Pilot Plant, Mass Spectrometry Center of the Biochemistry Department, as well as the National NMR Facility at Madison (NMRFAM). The breadth and depth of the applicant's training encompasses work in molecular biology, biochemistry, genetics, and structural chemistry. The training the applicant will receive is no different from any of other members of the sponsor's laboratory.